I'm due to rejoin by Monday.' Farrell's expression darkened.
'You see what keeps me ?' he said, sharply, striking his left knee with the flat of his hand.

'I had a bad fall, shooting in Scotland, years ago--when I was quite a lad.

Something went wrong in the knee-cap.

The doctors muffed it, and I have had a stiff knee ever since.

I daresay they'd give me work at the War Office--or the Admiralty.